442 Transactions. 



one mile north of Pahi also contains an abundance of calcified, sponge 

 spicules, and a re-examination of the limestone from Wellsford, and from 

 Limestone Island, in Whangarei Harbour, shows that calcined sponge 

 spicules are frequent in those rocks also. 



Thus in this group of rocks, Amuri limestone and hydraulic limestone, 

 which have always been correlated together, we have the following records 

 of the occurrence of the skeletons of siliceous organisms : — 



(1.) Diatomaceous and radiolarian ooze: (a) Kaiwaka, (b) Batley, 



(c) Oamaru (immediately beneath the polyzoal limestone). 



(2.) Globigerina ooze with Eadiolaria : (a) Kaikoura, (b) Amuri Bluff. 



(3.) Globigerina ooze with sponge spicules usually calcified : (a) Pahi, 



(b) Kaiwaka, (c) Port Albert, (d) Wellsford, (e) Limestone 



Island, Whangarei. 



It is thus evident that siliceous organisms have contributed to some 



extent in many localities to the material of the Amuri limestone and 



hydraulic limestone, and that at times the siliceous remains occur to the 



exclusion of all other material. It is certainly true that at Ward and in 



many other localities where the limestones have the hard siliceous character 



the remains of siliceous organisms have not yet been distinctly recognized. 



A further examination of the specimen from Ward seen after a study of the 



specimens from Batley makes it appear probable to me that diatoms and 



Eadiolaria are present, though much calcined and much destroyed by 



solution. In all the localities of the hydraulic limestone that have been 



mentioned there are also pronounced siliceous and flinty horizons. In view 



of the very general occurrence of the remains of organisms with siliceous 



skeletons, and of the fact that in many of the occurrences much of the 



siliceous matter is calcified, it is natural to come to the conclusion that the 



silica of these flinty rocks has been derived from the solution of the skeletons 



of siliceous organisms. 



The Auckland rocks called collectively hydraulic limestone appear to 

 have the same stratigraphical position as the Amuri limestone ■ — that is, 

 there are Cretaceous fossils below and Tertiary fossils in the strata that 

 rest on* them. The presence of radiolarian remains in some of these South 

 Island deep-sea rocks, and their similar stratigraphical position to the 

 hydraulic limestone, which almost certainly owes its frequent siliceous 

 character to organic skeletons, renders it probable that these South Island 

 flinty rocks also owe their siliceous contents to organic remains. In the. 

 light of our present knowledge this explanation seems more in accord with 

 those facts that we know than any hypothetical explanation based upon 

 the precipitation of silica from oceanic water. 



As thus described it will be seen that the whole series of yovmger rocks 

 in this district has near the base a limestone which is largely composed of 

 Foraminifera and is of relatively deep-sea orgin. For some time the sea 

 in which this limestone was deposited remained of considerable depth, but 

 the coast-line was sufficiently close to this locality to allow of the accumu- 

 lation of much terrigenous matter. The amount of sediment varied, and 

 from time to time it was reduced to such an extent and oceanic currents 

 changed so far as to allow of the deposition of greensands. At times tests 

 of Globigerina constituted the main portion of the deposit. During this 

 time ammonites with the affinities of species belonging to the Senonian 

 fauna were in existence, though the mollusca had something of a Cainozoic 

 aspect. There are also hard bands of limestone at various horizons which 

 contain species of Amphistegina and give to the formation more than ever 

 a Tertiary aspect. 



